PSI - Issue 84

Michela Pulsoni et al. / Procedia Structural Integrity 84 (2026) 214–222 M. Pulsoni et al. / Structural Integrity Procedia 00 (2026) 000–000

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images to be aligned (Slave) with respect to a reference image (Master). Co-registration therefore represents a crucial and indispensable step in photo-monitoring (Cosentino et al., 2022). All processing steps, from co-registration to the actual DIC or CD analysis, can be carried out within a single software environment, IRIS, developed by Nhazca S.r.l. IRIS is designed to work with terrestrial, aerial and satellite images acquired by any type of sensor (optical, thermal, near-infrared, radar, etc.) and includes several modules that allow the user to perform: • Pre-processing of the data (for the optimisation of input images). • Co-registration of images. • Change detection • Digital image correlation • Post-processing of the results (for the optimisation and enhancement of the final readability of the products). The results obtained are generally represented as thematic maps based on colour scales, which immediately display changes (in the case of CD analyses) and displacements (in the case of DIC analyses). The use of intuitive colour codings makes these maps easily interpretable even by non-expert users and represents a major operational advantage of photo-monitoring over other monitoring techniques, facilitating its adoption in different application and decision making contexts. 2.3. Ground-Based Interferometry (TInRAR) Ground-Based Radar Interferometry (TInRAR) is a remote sensing technique that enables the simultaneous measurement of displacements at numerous points belonging to buildings, infrastructures and other anthropogenic or natural elements. Thanks to the high achievable data sampling rates, the technique allows both static and dynamic analyses to be performed, including the measurement of structural vibrations. The measurements are carried out completely remotely, without the need to install sensors or reflectors in contact with the structure, exploiting the natural microwave backscatter of the objects present within the illuminated scenario. The TInRAR sensor consists of a coherent real-aperture interferometric radar, i.e. capable of transmitting radar pulses at a known wavelength, equipped with one or more transmitting and receiving antennas. The interferometric technique makes it possible to estimate displacements along the radar line of sight (LOS) by comparing the phase information of the transmitted and backscattered electromagnetic waves acquired at different times. The fundamental relationship linking the phase variation to the displacement along the LOS is shown in Fig. 2, together with a conceptual scheme of the measurement principle.

Fig. 2. Schematic Fundamental relationship for TInRAR and conceptual scheme measurement principle.

For each range resolution cell, two fundamental parameters can be derived: • Amplitude, which provides indications on the capability of the targets present within the investigated scenario to reflect the radar signal. • Phase, which allows the estimation of displacements through the comparison of acquisitions collected at different time intervals. Objects within the same range resolution cell cannot be individually distinguished and contribute to a single backscattered signal. Current TInRAR systems typically operate from a few hundred metres to several kilometres.